This training application is an interdepartmental and interdisciplinary program in Molecular Epidemiology in Children's Environmental Health (MECEH). Participating training faculty are from three interactive departments and include the Departments of Environmental Health, Pediatrics, and Molecular Genetics. The program focus is to identify outstanding pre-doctoral, and postdoctoral M.D.s and Ph.D.s and equip each with the knowledge base to undertake epidemiological and clinical studies using molecular markers of exposure, effect and susceptibility. These studies will examine the impact of environmental exposures on complex diseases in children's health. The program will provide training at three levels: the pre-doctoral student achieving a Ph.D. degree, the postdoctoral trainee with a Ph.D., and the M.D. postdoctoral pediatric resident seeking a M.S. degree in epidemiology. Entering pre- doctoral trainees will have the equivalent of an undergraduate degree majoring in biology, molecular biology, molecular genetics, mathematics or a related field having obtained superior academic achievements and a GRE of 1800 or better. Postdoctoral candidates must have proven academic accomplishments and hold the degrees of Ph.D. or M.D. The physicians should have completed three years their pediatric residency and have demonstrated scholarship. All trainees will have a specific interest in the use of cutting-edge molecular methods to understand the impact of environmental exposures on children's health. Requested for the first year are 2 pre-doctoral, 1 postdoctoral Ph.D. and 2 postdoctoral M.D. trainees. The physical facilities all contain modern well-equipped laboratories and computer facilities. Being one of 21 NIEHS Centers and the first Center for Environmental Genetics, the trainees are provided with optimum laboratory resources in a highly collaborative environment. Nationally, the MECEH program fulfills a critical need to train researchers at the pre-doctoral and postdoctoral levels with combined understanding and research skills in pediatric epidemiology, biostatistics, molecular biology and toxicology, and genetics. Institutionally, this program will further collaborations and empower trainees to utilize the best scientific approaches that these disciplines offer.